Remove the file pattern to use the default list

This is an intended behaviour change. With this commit, also source
files (*.cpp) are scanned for doxygen documentation. This was necessary
to recognize \file tags in samples and tests source files.

refs #594

docs/Doxyfile.qmake

@@ -784,23 +784,7 @@ INPUT_ENCODING         = UTF-8
 # *.md, *.mm, *.dox, *.py, *.f90, *.f, *.for, *.tcl, *.vhd, *.vhdl, *.ucf,
 # *.qsf, *.as and *.js.
 
-FILE_PATTERNS          = *.ii \
-                         *.ixx \
-                         *.ipp \
-                         *.i++ \
-                         *.inl \
-                         *.inc \
-                         *.h \
-                         *.hh \
-                         *.hxx \
-                         *.hpp \
-                         *.h++ \
-                         *.idl \
-                         *.m \
-                         *.markdown \
-                         *.md \
-                         *.mm \
-                         *.dox
+FILE_PATTERNS          =
 
 # The RECURSIVE tag can be used to specify whether or not subdirectories should
 # be searched for input files as well.